Corrosion Inhibition of Mild Steel in Acidic Media by 5′-Phenyl-2′,4′-dihydrospiro[indole-3,3′-pyrazol]-2(1H)-one

Table 5

Potentiodynamic polarization parameters for the corrosion of mild steel in 1 M HCl and 0.5 M H₂SO₄ with and without inhibitor.

Name of the inhibitor	Inhibitor concentration (ppm)	𝐼corr; (μA/cm^2) × 10^2	𝐸corr; (mV versus SCE)	𝛽c (mV/dec)	𝛽a (mV/dec)	Inhibition efficiency (%)
1 M HCl	Blank	1.6759	−555.68	149.91	89.961
	1	1.3797	−543.91	157.94	92.412	17.67
SPAH	5	1.1145	−550.84	130.20	83.362	33.49
	9	9.5813	−544.70	150.50	90.651	42.82
0.5 M H2SO4	Blank	16.99	−444.62	113.48	231.18
	1	9.1947	−536.55	273.62	123.04	45.88
SPAH	5	6.2370	−534.52	249.93	101.00	63.29
	9	5.6636	−534.78	229.22	97.09	66.66